Throw-away type air filters have been on the market for many years. These throw-away air filters have been made for both consumer and commercial use in HVAC systems. These inexpensive filters provide protection mainly for the HVAC system itself. These filters are provided so that large objects are captured before they can cause damage to the fan motor and other components. In general, these low-efficiency filters were not intended to capture smaller particles of dust, pollen and mold that pass through to the indoor environment.
A very large number of permanent-type air filters have recently entered the market. These permanent-type air filters are generally made of a rigid aluminum frame. The filter material is received between two walls of expanded metal material. The filter material is made of a very pliable material having little or no interior strength. The expanded metal material can be used to form a honeycomb shape around the filter material. The expanded frame is used to support the filter material within the frame.
There have been several types of signalling devices for air filters on the market for some time. Some of these devices feature whistle holes. It is known from U.S. Pat. No. 2,753,831, to Davies, to provide an air filter clogging warning apparatus in which a whistle is secured within a tube which extends through the filters, the tube being affixed in the filter by a funnel-shaped portion at its upstream end and a washer affixed adjacent its downstream end. This patent also contemplates the provision of screen over the mouth of the funnel-shaped end of the tube. It is also known to provide whistles and vibrating reed warning devices in conjunction with carburetor air intake filters so as to signal when the filters are clogged and in need of replacement. Various patents have described such a device, including U.S. Pat. Nos. 1,770,094 to Wickersham; U.S. Pat. No. 1,863,456 to Smith; and U.S. Pat. Nos. 3,529,407, 3,699,749, 3,737,900, and 3,740,931 to Nowicki.
U.S. Pat. No. 4,321,070, issued on Mar. 23, 1982, to J.D. Bede describes a whistling device that has a simple two-part construction molded of plastic material. This device includes a first flanged part which is inserted through the filter from the upstream end thereof and with a disk-like part being snapped over the downstream end of the first part so as to constitute a flange on the downstream side of the filter and to form a whistle at the downstream end of the filter which emits a shrill tone when the pressure drop across the filter reaches a predetermined value. When a clogged condition of the filter is indicated, the two-part whistle therein may be quickly and easily removed from the clogged filter and reinserted into a new filter for reuse.
In General, these devices were designed for low efficiency type "throw-away filters", and as a result, they were specifically designed to be interchanged from one filter to another. As the old dirty filter was removed and discarded, a new clean filter was installed. These devices, especially U.S. Pat. No. 4,321,070 to Bede, were made in a round cylindrical configuration, in order to fit snugly into the round holes commonly found in the outer aluminum mesh of throw-away filters. Therefore, the Bede device, in particular, had to be both round and of a two piece, removable design.
This type of design, although adequate for throw-away filters, is undesirable for permanent/reusable type filters, due to the likelihood that the noise maker could be removed from the filter, or otherwise fall out of the filter as the consumer performs periodic washing that is required for permanent filters. This would leave the filter with a large, gaping hole through which a great amount of dust and other debris could pass.
Typically, the whistle hole in these devices was manufactured in a permanently open position. This was not of much significance in "low efficiency" air filters, as these types of filters normally capture only a small percentage of airborne dust and contaminants. Therefore, the presence of an opening in the whistle device was not much of a detriment to the overall ability of the filter to perform its function. However, this "open hole" configuration is undesirable for permanent/reusable filters, as these types of filters are normally "high efficiency" filters; designed to capture a much greater amount of dust and other contaminants than common throw-away filters. Therefore, the open whistle hole allows an unacceptable amount of dust and dirt to be sucked through the noise maker, totally bypassing the fine filtering materials intended to arrest such particles.
Another disadvantage of these previous noise makers is their inherently round design. This design precludes the possibility of having any type of easily differentiated "up" position of the noise maker relative to the sides of the filter. Such a configuration would be necessary for the optimum performance of a noise maker device.
The whistle holes of existing noise makers for air filters are manufactured in only one size. This is not very effective for actual working conditions. Typically, the fan/filter size combination, found in the average home, can vary dramatically. As a result, a household with a particularly large fan relative to the filter size will typically experience a whistle sound before the filter has become even lightly clogged. Conversely, a household with a particularly small fan relative to the filter size will not ever detect a whistle tone from the noise maker, even when the filter is completely clogged.
It is an object of the present invention to provide a noise maker device that is constructed of one-piece construction which cannot be opened or disassembled.
It is another object of the present invention to provide a noise maker device that has a relatively square design so as to be easily marked so as to indicate which direction is "up", relative to the sides of the filter into which it is affixed.
It is another object of the present invention to provide a noise maker device having a suitable means for keeping the whistle hole closed until the filter becomes clogged.
It is a further object of the present invention to provide e noise maker device having a whistle hole of variable size such that the Whistle hole can be adjusted for the desired sound level for all types of fan or filter combinations in residential homes and commercial structures.
It is still a further object of the present invention to provide a noise maker device that is indicative of a clogged condition of en air filter.
It is still another object of the present invention to provide a noise maker device that is relatively inexpensive, easy to operate, and easy to manufacture.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.